As noted in U.S. Pat. No. 5,560,972, carpet construction can vary but generally a pile carpet is manufactured in one of two ways. The pile yarn may be woven or tufted through a primary backing. The yarn is then secured to the primary backing with adhesive. This type of carpet in which yarn is mechanically as well as adhesively attached to backing is generally termed “woven” or “tufted” carpet. Alternatively, yarn may be cut or looped and positioned to form a pile layer that is then secured to the primary backing with adhesive. Carpet of this type of commonly referred to as “fusion bonded” carpet.
Fusion bonded carpet is generally categorized by the way the pile yarn layer is produced. In an “I-tuft” process, yarn is first cut into short, straight strands, and then the yarn ends are bonded to a primary support backing with adhesive. In a “U-tuft” process, a pile yarn layer is formed of folded yarn strands. The folded sections of the strands are then secured to the primary backing with an adhesive layer such that in the final carpet product, both ends of each cut strand protrude from the adhesive base.
Fusion bonded carpets typically use a non-latex polyvinyl chloride (PVC) plastisol formulation as the bonding adhesive layer that penetrates into the support layer. The adhesive layer is then contacted with pile forming yarn. The PVC plastisol is cured, creating a product in which the yarn fibers are secured in the PVC later and thereby bonded to the support layer. Increased strength may be obtained by bonding the secondary backing to the support layer.
In order to make a durable fusion bonded carpet in which the support layer does not peel away from the secondary backing, the adhesive which has permeated into the support layer must contact and bond with the material forming or adhering the secondary backing. The use of a non-latex plasticized PVC as the yarn locking adhesive limits the variety of backing structures that may be applied to the carpet. This is true because non-latex PVC plastisol does not bond strongly to common carpet backing materials such as bitumen, EVA (ethylene-vinyl acetate), APP (atactic polypropylene), hot melts, urethanes, and SBR (styrene-butadiene). Furthermore, SBR (styrene-butadiene) is relatively expensive, and PVC plastisol is both relatively expensive and presents environmental concerns due to its chloride content.
A fusion bonded carpet which does not use PVC as the pile yarn adhesive is described in U.S. Pat. Nos. 4,371,576 and 4,576,665. The carpet is prepared by forcing a heated hot melt adhesive through a liquid permeate support layer to contact with the pile forming yarn on the opposite side of the base layer. The adhesive is then allowed to cool, during which time the pile forming yarn and support layer are secured.
Hot melt adhesives have been known for many years and usually include a thermoplastic resin, wax and a polymeric adhesive. Hot melt adhesives are applied at high temperature, and cured at cooling.
U.S. Pat. No. 3,775,366 discloses a process for crosslinking compounds by exclusively using triazines as the crosslinking agent for natural and synthetic rubbers. More specifically, the '366 patent relates to a process of cross-linking synthetic rubber containing fillers or mixtures containing these materials without the use of elemental sulfur with heat and possibly pressure.
U.S. Pat. No. 5,206,304 describes the use of bis(2,4-organylthio-s-triazine-6-yl) polysulfides as accelerators in vulcanizable rubber mixtures including SBR. The bis(2,4-organylthio-s-triazine-6-yl) polysulfides in the '304 patent are described as rubber mixtures such as those customarily used in tire construction and to industrial articles such as e.g. mixtures for conveyor belts, V belts, molded articles, hoses with and without linings, rubber coatings for rollers, jacketings, injection profiles, free-hand articles, foils, shoe soles and top parts, cables, all-rubber tires and their vulcanizates.
U.S. Pat. No. 5,560,972 discloses a fusion bonded carpet in which the pile yam is secured in a non-hot-melt latex adhesive base and methods of manufacture of such carpet. The viscosity of the latex formulation (latex polymer in aqueous solution) is described as ranging from 20,000-150,000 cps (centipoise), with an optimal range of 40,000-120,000 cps. Claim 1 of the '972 patent describes a latex bonded carpet that can include a non-hot melt latex adhesive base; wherein the latex adhesive has a viscosity ranging between 40,000 and 150,000 cps prior to any curing, and wherein the non-hot melt latex adhesive can include vinyl acetate-ethylene, ethylene-vinyl acetate and styrene-butadiene all as part of the latex adhesive itself.
U.S. Patent Publication Number 20080113146 pertains to carpet and methods of making and recycling carpet. In one aspect, the carpet includes: a primary backing which has a face and a back surface; a plurality of fibers attached to the primary backing and extending from the face of the primary backing and exposed at the back surface of the primary backing; an adhesive composition backing; and an optional secondary backing adjacent to the adhesive backing. In claim 37 of the '146 patent publication, a pre-coat material as claimed recites a combination of VAE emulsion and SBR latex.
There remains a need for bonding agents with improved flow properties and improved strength and physical properties when compared to the conventional binder system for carpets.